awneil
1
To be able to send an SMS, a device must have a valid Service Centre Address, SCA (aka Message Centre phone number, etc)
When reading a message in PDU mode, an SCA is included - Is it safe to assume that this SCA will be valid for use to send any reply 
From my experience you don’t need to specify the SCA with most operators nowadays anymore…
awneil
3
I agree - but “most” is not sufficient!
